Electronic discharge device



June29, 1943- A. F. SHORT ELECTRONIC DISCHARGE DEVICE Filed March 14, 1945 Patented June 29, 1948 ELECTRONIC DISCHARGE DEVICE Arthur F. Short, West Newton, Mass, assignor to Raytheon Manufacturing Company, Newton, Mass, a corporation of Delaware Application March 14, 1945, Serial No. 582,666

6 Claims. (01. 250-275) This invention relates to an electronic discharge device of the magnetron type, and more particularly to the seal structure for the lead-in conductors providing the electrical connections and supports for the cathode and heater elements of such devices.

In devices of this type the cathode and its heater form a unitary structure which must be accurately positioned with respect to the anode Structure. In tubes of this kind, the lead-in connectlons for the cathode are disposed laterally of the tube so as not to interfere with the means for imposing the longitudinal field between the cathode and the anode, which causes the device to function as a magnetron. Any vibration of the lead-in conductors results in a corresponding vibration of the cathode structure relative to the anode, and thus introduces undesirable variations into the operation of the device. Furthermore, such vibration tends to introduce strains in the glass structure which may result in fracturing said structure. Also excessive vibrations tend to cause the lead-in conductors to approach surrounding metallic portions to which short-circuiting may occur.

An object of this invention is to devise a seal structure for the lead-in conductors of the cathode which will afford a support in which vibrations and motions of the above undesired type are substantially eliminated.

The above and other objects of this invention will be best understood from the following description of an exemplification thereof, reference being had to the accompanying drawing, in which Fig. 1 is a transverse section of a magnetron embodying my invention; and

Fig. 2 is a cross-section through the seal structure, taken along line 2-2 of Fig. 1.

The magnetron illustrated in the drawing comprises a tubular envelope I made of a cylinder of conducting material, such as copper. The ends of the envelope are covered by caps 2 and 3 likewise formed of conducting material, such as copper, and hermetically soldered in place on the ends of the envelope I. The envelope l is formed with a central annular projection 4. A plurality of radial plates 5 are soldered in place along the inner surface of the projection 4. These plates may be stamped out of a sheet of highly-conductive copper. The inner ends of the plates 5 form anode faces which cooperate with a cathode 6 supported substantially centrally of said anode faces. The cathode 6 is preferably of the indirectly-heated oxide-coated thermionic type having an outer conducting cylinder 1 coated with an electron-emissive oxide layer 8, and having an internal heater 9, the end conductors l0 and I l of which project from the opposite ends of the cathode structure 5. In order to support and insulate the heater from the cylinder 7, a pair of insulating plugs l2 and I3 are inserted in the opposite ends of the sleeve 1. The end conductors l0 and l I pass through openings in these insulating plugs. A pair of conducting straps M are welded to the upper end of the sleeve I, extend across the outer surface of the insulating plug l2, and are in turn welded to the end conductor ID. This retains the end conductor l0 and the heater 9 in place, and also electrically connects theend conductor H] to the sleeve 1. The lower insulating plug is retained in place by a pair of strips I 5 welded in placefat the lower end of the conducting sleeve 'I. These strips, however, do not come into electrical contact with the end conductor l l which is thus insulated from the sleeve 1 The cathode is supported and provided with external electrical connections by means of a pair of cathode and heater lead-in conductors l6 and I7. The conductor 16 is rigidly and electrically connected to the end conductor l0, while the conductor I1 is rigidly and electrically connected to the end conductor II. The lead-ins l6 and l! are sealed respectively through glass tubes l8 and I9 sealed atthe outer end of conducting pipes 20 and 2|, hermetically fastened through the wall of the envelope I adjacent the upper and lower ends thereof.

When such a magnetron is placed between suitable magnetic poles 22 and 23 to create a longitudinal magnetic field and the device is energized, oscillations are set up. These oscillations may be led out from the tube by means of a coupling loop (not shown), extending into the space between two of the plates 5.

In order to reduce the free length of the conductors l6 and I1 from the cathode structure to the points at which they are supported, reentrant glass tubes 24 and 25 are sealed in the outer ends of the glass tubes l8 and Hi. The conductors I6 and ii are sealed through the inner ends of the tubes 24 and 25, respectively, by seals 26 and 21. Beyond the seals 26 and 21, protective glass sleeves 28 and 29 surround the conductors I6 and I 1, respectively. These protective sleeves tend to prevent arcing from the ends of the metal .pipes 20 and 2| to the conductors to and H as said conductors enter said pipes.

It will be noted that although the conductors l6 and I! are supported at the seals 26 and 21,

nevertheless any tendency which exists for the cathode structure and its lead-in conductors to vibrate will introduce a substantial strain at the outer ends of the tubes I8 and I9 where the tubes 24 and 25 are sealed thereto. Furthermore, any flexibility of the glass which exists at this point will tend to permit undesired motion and vibration of the cathode structure to occur. In order to prevent this, the outer tubes l 8 and I9 are each provided with a plurality of indentations or dimples '30 which project inwardly into the space surrounded by said tubes. These dimples are preferably three in number. The protective sleeves 28 and 29 are each provided with an enlarged section 3|, the outer diameter of which is slightly larger than the diameter of the free space left between the dimples 30.

The tubes l8 and I9 are initially made separate from the tubes 24 and 25. When the tubes and 25 carrying the rods I B and l! are initially inserted in the ends of the tubes 18 and i9, they can project into said tubes l8 and 19 until the enlargements 3| contact the dimples 30. The parts are so arranged that in this location the inner ends of the conductors I 6 and I! project the proper distance through the pipes 20 and 2 I. The tubes 18 and I9 are then sealed to the tubes 24 and 25, respectively, in this position. While the glass is still soft the tube i8 is drawn out slightly so that the resulting structure, which is shown in the drawing, is one in which the enlargements 3| are spaced .a very slight distance from the dimples 39. Thus in the final form of the tube, the enlargements 3| and the dimples 30 cooperate to prevent excessive vibration of the cathode structure. Thus the cathode structure is accurately supported in the proper position within the tube. Also there is substantially no danger of the conductors i6 and I! shorting against the tubes 20 and 2| nor is there any substantial tendency for fracturing of the glass structure to occur where the tubes l8 and I9 are sealed to the tubes 24 and 25, respectively.

Of course it is to be understood that this invention is not limited to the particular details as described above, inasmuch as many equivalents will suggest themselves to those skilled in the art. It is accordingly desired that the appended claims be given a broad interpretation commensurate with the scope of the invention within the art.

What is claimed is:

1. An electron discharge device comprising an envelope, a cathode-heater structure, a, pair of lead-in conductors connected to opposite ends of said cathode-heater structure providing supports therefor, a pair of conducting tubes projecting externally of said envelope, said lead-in conductors extending through said conducting tubes and out of contact therewith, glass seals closing the outer ends of said conducting tubes, said seals having tubular portions projecting outwardly from said conducting tubes, and reentrant stems projecting back into said tubular portions sealing and supporting said lead-in conductors therein, said reentrant stems being spaced from the inner walls of said tubular portions, said tubular portions each having an indented wall portion ad jacent the outer portion of the reentrant stem to restrain said stem and its conductor from excessive motion relative to said tubular portion.

2. An electron discharge device comprising an envelope, a cathode-heater structure, a lead-in conductor connected to one end of said cathodeheater structure providing a support therefor, a

conducting tube projecting externally of said envelope, said lead-in conductor extending through said conducting tube and out of contact therewith, a glass seal closing the outer end of said conducting tube, said seal having a tubular portion projecting outwardly from said conducting tube, and a reentrant stem projecting back into said tubular portion sealing and supporting said lead-in conductor therein, said reentrant stem being spaced from the inner wall of said tubular portion, said tubular portion having an indented wall portion adjacent the outer portion of the reentrant stem to restrain said stern and its conductor from excessive motion relative to said tubular portion.

3. An electron discharge device comprising an envelope, a cathode-heater structure, a, lead-in conductor connected to one end of said cathodeheater structure providing a support therefor, a conducting tube projecting externally of said envelope, said lead-in conductor extending through said conducting tube and out of contact therewith, a glass seal closing the outer end of said conducting tube, said seal having a tubular portion projecting outwardly from said conducting tube, and a reentrantstem projecting back into' said tubular portion sealing and supporting said lead-in conductor therein, said reentrant stem being provided with a protectiveglass sleeve projecting beyond said seal into said conducting tube and surrounding said lead-in conductor.

4. An electron discharge device comprising an envelope, a cathode-heater structure, a lead-1n conductor connected to one end of said cathodeheater structure providing a support therefor, a conducting tube projecting externally of said envelope, said lead-in conductor extending through said conducting tube and out of contact therewith, a glass seal closing the outer end of said conducting tube, said seal having a tubular portion projecting outwardly from said conducting tube, and a reentrant stem projecting back into said tubular portion sealing and supporting said lead-in conductor therein, said reentrant stem being spaced from the inner wall of said tubular portion, said reentrant stem being provided with a glass sleeve projecting beyond said seal and surrounding said lead-in conductor, said glass sleeve being provided with a bulged portion, said tubular portion having an indented wall portion adjacent the said bulged portion to restrain said stem and its conductor from excessive motion relative to said tubular portion.

5. An electron discharge device comprising an envelope, a cathode-heater structure, a lead-in conductor connected to one end of said cathodeheater structure providing a support therefor, a conducting tube projecting externally of said envelope, said lead-in conductor extending through said conducting tube and out of contact therewith, a glass seal closing the outer end of said conducting tube, said seal having a tubular portion projecting outwardly from said conducting tube, and. a reentrant stem projecting back into said tubular portion sealing and supporting said lead-in conductor therein, said reentrant stem being spaced from the inner wall of said tubular portion, said tubular portion having a plurality of indentations projecting within it, said indentations beingedjacent the outer portion of the reentrant stem to restrain said stem and its conductor from excessive motion relative to said tubular portion.

6. A sealing structure comprising :an outer tubular membenand an inner tubular member supported by said outer tubular member coaxially REFERENCES CITED therewith, said outer tubular member having an indented portion, and said inner tubular member The following references are of record in the having an enlarged portion cooperable-with said file Of this D nti indented portion to restrict relative movement 5 UNITED STATES PATENTS between said outer and inner tubular members.

Number Name Date SHORT. Gibson et a1 July 3, 

